1. Field of the Invention
The present invention relates to an image display apparatus and an image display method for displaying image data acquired by an image diagnostic apparatus such as an X-ray CT (computed tomography) apparatus, and more particularly, to an image display apparatus and an image display method which can generate image data of a desired portion with an appropriate resolution and display form efficiently to be displayed.
2. Description of the Related Art
An X-ray CT apparatus is one of image diagnostic apparatuses in the medical field (see, for example, Japanese Patent Application (Laid-Open) No. 2000-139897). The X-ray CT apparatus is mainly connected to a 3D-WS (three-dimensional workstation) for performing image processing of an obtained X-ray CT image, an image server for storing images, and an image display apparatus for displaying the images to be capable of communicating data with each other via an image display network, and forms an X-ray CT image diagnostic display system. A system including the image display apparatus and the image server is called a medical PACS (picture archiving and communication system).
FIG. 15 is a block diagram of a conventional X-ray CT image diagnostic display system.
An X-ray CT image diagnostic display system 1 includes: an X-ray CT apparatus 2; a 3D workstation 3; an image server 4, serving as an image storage apparatus; and an image display apparatus 5, serving as an image viewer.
The X-ray CT apparatus 2 performs the scan operation, and a detector 6 detects X rays which are exposed from an X-ray tube (not shown) and pass through an object. After that, a raw data storage unit 7 stores the X-ray data, as raw data. An image reconstructing unit 8 reads the raw data stored in the raw data storage unit 7 and performs image reconstruction processing of the read raw data. Thus, cross-sectional data (hereinafter, referred to as slice image data) is generated and is written to a reconstructed image storage unit 9. Herein, with a 3D image generating unit 10, a user, e.g., an engineer generates relatively simple 3D image data including an MPR (multi-planar reconstruction) image and an MIP (maximum intensity projection) image from the slice image data, as needed. The generated 3D image data is written to and is stored to the reconstructed image storage unit 9.
Subsequently, the slice image data and the 3D image data is transmitted to the image server 4 and the 3D workstation 3 from the reconstructed image storage unit 9 via a communication unit 11 and a network 12. A communication unit 13 in the 3D workstation 3 receives thin-slice image data generated by the X-ray CT apparatus 2, and the received thin-slice image data is written to and is stored to a 3D image storage unit 14. Further, a 3D image generating unit 15 generates, from the thin-slice image data, relatively advanced 3D image data, such as VR (volume rendering) image data, SSD (surface shaded display) image data, and VE (virtual endoscopy) image data. The generated 3D image data is written to and is stored to the 3D image storage unit 14. Further, a display unit 16 displays the thin-slice image data and the 3D image data.
Note that the thin-slice image data corresponds to a slice image with such a thickness that an XY planar resolution of the image is approximately equal to the Z direction (thickness). The above-mentioned image pixel can be used as isotropic voxel and is therefore suitable to the 3D image processing. It is assumed that image data of the slice image of about 0.5 mm to 2 mm is used as the thin-slice image data.
Further, the above-generated 3D image data is transmitted to the image server 4 via the communication unit 13 and the network 12. A communication unit 17 in the image server 4 receives the slice image data and the 3D image data transmitted from the X-ray CT apparatus 2 and the 3D image data transmitted from the 3D workstation 3. The received slice image data and 3D image data is written to and is stored to an image storage unit 18. A recording unit 19 reads the image data stored in the image storage unit 18, as needed. The read data is recorded to a recording medium 20. In this case, administration information, e.g., a recording history of the image data is transmitted to an administration unit 21. The administration unit 21 administrates the image data stored in the image storage unit 18 and the image data recorded to the recording medium 20 from the recording unit 19.
Subsequently, an input unit 22 in the image display apparatus 5 inputs a retrieving request and a transmitting request of the image data. The retrieving request and the transmitting request are transmitted to the administration unit 21 in the image server 4 via a communication unit 23 and the network 12. Therefore, the administration unit 21 reads desired image data from the image storage unit 18 and transmits the image data to the communication unit 17, thereby transmitting the image data to the image display apparatus 5.
The communication unit 23 in the image display apparatus 5 receives the slice image data transmitted form the image server 4, and transmits the received slice image data to a display unit 24. As a consequence thereof, the display unit 24 displays the slice image in a tile or stack format which is used for interpretation.
Mainly, the image display apparatus 5 for interpretation uses such a 2D viewer that the image data received from the image server 4 is simply arranged as mentioned above, or is browsed and is displayed. Recently, the image display apparatus 5 for interpretation frequently uses a viewer with a 3D function for generating 3D image data.
Further, a large number of pieces of the slice image data is recently subjected to MPR processing with the 3D workstation 3, a coronal tomographic image (coronal image) and a sagittal image are thus generated, and 3D processing, such as MIP processing, is performed. In addition, the efficiency and quality of diagnosis is improved with clinical analysis application for the clinical analysis, such as the analysis of the coronary-artery and the analysis of the heart function based on the 3D processing technology.
Data with high resolution, that is, a large amount of the thin slice data is necessary for generation of a 3D image, e.g., an MPR image with high image quality and for clinical analysis with high precision. However, the generation and storage of a large amount of the slice data results in the consumption of a large amount of disk resource of the image display apparatus 5 and the image server 4. This is not preferable in view of costs.
In order to solve the problem, in the imaging operation for the purpose other than that of generating the 3D image, the X-ray CT apparatus 2 outputs only the thick slice data and the MPR image and the only affected part is used as the thin slice data. However, the method is performed on the basis of engineer's determination in the imaging operation. Therefore, there is a problem that causes a danger in which a doctor cannot refer to the image data with necessary precision in the interpretation.
Further, in the interpreting technique of the CT image, the diagnostics based on the axial image has been established for a long time. The MPR image and the 3D image are used as images that support the diagnosis and, finally, the diagnosis is necessarily performed on the basis of the slice data. However, the conventional image display method has a large number of images of the slice data and, therefore, there is a danger of the deterioration in efficiency of the interpretation.
In particular, the number of rows recently increases in the multi-slice CT apparatus, and a numerous amount of image data is generated. Therefore, a method for efficiently displaying an image of a desired portion with a proper resolution and a proper display form is required. However, in order to efficiently use data communication resource and data storage resource, unnecessary generation of the slice data needs to be prevented.